This invention relates generally to backplane system architecture, and more specifically to a free space optical backplane configuration.
A communications system backplane provides a common bus having sockets through which switch cards and line cards may be connected to the other parts of the system. Typical wired backplanes use a particular type of architecture such as Asynchronous Transfer Mode (ATM), Internet Prototcol (IP), or other types of packet-based architecture. The drawback of such a scheme is that the particular bandwidth is set. Recent improvements in backplane architecture include the implementation of an optical backplane. An optical backplane has the advantage of providing much higher bandwidth capacity. An optical backplane can be implemented having scalable bandwidth and can take advantage of technologies such a dense wave division multiplexing (DWDM) to increase bandwidth and add flexibility to the system. Additionally, faster optical interfaces are being developed.
A disadvantage to typical optical backplanes is the amount of space they take up within the chassis. FIG. 1 illustrates the configuration of two cards, within a chassis, optically connected according to the prior art. The system 100 shown in FIG. 1 has two, for example, line cards 102a and 102b. Line cards 102a and 102b each have a laser transceiver 104a and 104b, respectively. Attached to laser transceiver 104a is a length of optical fiber known as a xe2x80x9cpigtailxe2x80x9d 106a. Pigtail 106a couples the laser transceiver 104a to a transition connector 108a that is coupled to a bulkhead 110a and likewise to another transition connector 112a. This interconnecting hardware takes up a great deal of space within the chassis. Transition connector 112a is connected to transition connector 112b via transmission fiber 114. Transmission fiber 114 has a bend radius associated with it that is typically measured in inches. Transition connector 112b is coupled to bulkhead 110b and likewise to another transition connector 108b. Accommodating an optically interconnected backplane requires an excessive amount of the area of the card as well as the chassis. For example, the interconnecting hardware, together with the bend radius of the transmission fiber, requires from 2.5 to 3 inches of chassis space in a system typically having a 12-inch chassis.
A system allowing free-space optical data transmission is disclosed. The system is has a chassis having a plurality of card slots with at least one switch card having a plurality of switch card laser transmitters and a plurality of switch card photodetectors, inserted into a card slot. The system has at least one feature card having a feature card laser transmitter and a feature card photodetector, inserted into a card slot. The system has an alignment mechanism to align the at least one feature card such that the feature card laser transmitter aligns with a specified switch card photodetector and the feature card photodetector aligns with a specified switch card laser transmitter. The system also has a free-space optical data transmission path such that the feature card laser transmitter can transmit a signal to the specified switch card photodetector and the specified switch card laser transmitter can transmit a signal to the feature card photodetector.
Other features and advantages of the present invention will be apparent from the accompanying drawings, and from the detailed description, which follows below.